//typedef struct my_custom_pbuf
//{
//   struct pbuf_custom p;
//   void* dma_descriptor;
//} my_custom_pbuf_t;
//
//LWIP_MEMPOOL_DECLARE(RX_POOL, 10, sizeof(my_custom_pbuf_t), "Zero-copy RX PBUF pool");
//
//void my_pbuf_free_custom(void* p)
//{
//  SYS_ARCH_DECL_PROTECT(old_level);
//
//  my_custom_pbuf_t* my_puf = (my_custom_pbuf_t*)p;
//
//  // invalidate data cache here - lwIP and/or application may have written into buffer!
//  // (invalidate is faster than flushing, and no one needs the correct data in the buffer)
//  invalidate_cpu_cache(p->payload, p->tot_len);
//
//  SYS_ARCH_PROTECT(old_level);
//  free_rx_dma_descriptor(my_pbuf->dma_descriptor);
//  LWIP_MEMPOOL_FREE(RX_POOL, my_pbuf);
//  SYS_ARCH_UNPROTECT(old_level);
//}
//
//void eth_rx_irq()
//{
//  dma_descriptor*   dma_desc = get_RX_DMA_descriptor_from_ethernet();
//  my_custom_pbuf_t* my_pbuf  = (my_custom_pbuf_t*)LWIP_MEMPOOL_ALLOC(RX_POOL);
//
//  my_pbuf->p.custom_free_function = my_pbuf_free_custom;
//  my_pbuf->dma_descriptor         = dma_desc;
//
//  invalidate_cpu_cache(dma_desc->rx_data, dma_desc->rx_length);
//
//  struct pbuf* p = pbuf_alloced_custom(PBUF_RAW,
//     dma_desc->rx_length,
//     PBUF_REF,
//     &my_pbuf->p,
//     dma_desc->rx_data,
//     dma_desc->max_buffer_size);
//
//  if(netif->input(p, netif) != ERR_OK) {
//    pbuf_free(p);
//  }
//}
